1. Field of the Invention
This invention relates generally to tools used to complete subterranean wells. More particularly the present invention describes a means of completing two zones within a single wellbore with the capability of isolating one of the zones.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The problems caused by sand production can significantly increase operational and maintenance expenses and can lead to a total loss of the well. One means of controlling sand production is the placement of relatively large sand (i.e., xe2x80x9cgravelxe2x80x9d) around the exterior of a slotted, perforated, or other type liner or screen. The gravel serves as a filter to help assure that formation fines and sand do not migrate with the produced fluids into the wellbore.
In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated formation that is to be completed for production. The screen is typically connected to a tool that includes a production packer and a cross-over, and the tool is in turn connected to a work or production tubing string. The gravel is mixed and pumped in a slurry down the tubing and through the cross-over, thereby flowing into the annulus between the screen and the wellbore. The liquid forming the slurry leaks off into the formation and/or through the screen, which is sized to prevent the gravel in the slurry from flowing through. The liquid that passes through the screen flows up the tubing and then the cross-over directs it into the annulus area above the packer where it can be circulated out of the well. As a result of this operation, the gravel is deposited in the annulus area around the screen where it forms a gravel pack. The screen prevents the gravel pack from entering into the production tubing. It is important to size the gravel for proper containment of the formation sand, and the screen must be designed in a manner to prevent the flow of the gravel through the screen.
In wellbores that penetrate more than one productive zone it is often desired to complete and produce more than one zone. In some cases more than one zone can be completed and produced together. This is often referred to as commingled production. In other cases, often due to differing reservoir characteristics such as formation pressures, two zones will be completed, but will be separated and produced through separate production strings. This is often referred to as a dual completion.
A common problem encountered when completing a well as a dual completion is a temporary commingling of the separate zones and the loss of substantial amounts of completion fluids into one or both of the formations, resulting in possible formation damage and requiring multiple trips into the wellbore to perform remedial treatments. The multiple trips and the remedial actions needed to reduce or remove formation damage can significantly increase the time and expense of dual well completions.
At times it is desirable to complete a zone and then isolate the zone until production is initiated or resumed at a later date. An example of this is when work is to be performed on the lower zone in a dual completion well; it may be beneficial to isolate the upper zone while the work is performed on the lower zone, both to increase safety during the well work and to reduce the chances of formation damage to the upper zone due to fluid loss. Zonal isolation systems are used to isolate and selectively produce oil or gas from separate zones in a single well. U.S. Pat. Nos. 5,579,844; 5,609,204 and 5,988,285 describe systems for the zonal isolation of wells. Often these systems involve multiple trips into the well and significant time and expense to perform. Any reduction in the number of trips required to complete a well or isolate a zone during subsequent operations can result in significant cost savings.
There is a need for improved tool assemblies and methods that enable the completing of a wellbore as a dual completion while reducing the chances of fluid loss into completed zones and enabling subsequent remedial work.
One embodiment of the present invention is a zonal isolation assembly for completing a first zone in a subterranean wellbore. The zonal isolation assembly comprises an inner housing and a sliding sleeve capable of moving between an open and closed position. The sliding sleeve is disposed within the inner housing. A passageway provides fluid communication between the inside and outside of the inner housing and an isolation tubing element is at least partially disposed within the inner housing and capable of moving between an upper position and a lower position. When the sliding sleeve is in its closed position and the isolation tubing element is in its lower position, fluid communication from the first zone through the isolation assembly is restricted.
The isolation tubing element can be releasably attached to the inner housing. The isolation tubing element can comprise a sealing element adapted to seat within a receptacle attached to a lower packer when the isolation tubing element is in its lower position. The receptacle can be releasably attached to the lower packer.
The assembly can further comprise an upper packer and an outer housing connected to the upper packer and to the lower packer. The outer housing can be connected to the inner housing and comprise a wall having a passageway therethrough, the outer housing and the passageway are located above the inner housing and below the upper packer. A sliding sleeve can be disposed within the outer housing capable of moving between an open and closed position and located above the inner housing. The outer housing can further comprise a sand screen located below the inner housing. The inner housing, isolation tubing element and receptacle can each be releasable disposed within the outer housing.
When the isolation tubing element is in its upper position, the isolation tubing element is capable of providing fluid communication between the area within the inner housing and the sand screen. When the isolation tubing element is in its lower position, the isolation tubing element is capable of providing fluid communication between the area within the inner housing and the area below the lower packer. When the isolation tubing element is in its lower position and the sliding sleeve disposed within the inner housing is in its closed position, fluid communication through the sand screen is restricted. When the isolation tubing element is in its lower position and the sliding sleeve disposed within the inner housing is in its closed position, the isolation tubing element is capable of providing fluid communication between the area within the outer housing located above the inner housing and the area below the lower packer.
When the sliding sleeve disposed within the outer housing is in its open position, fluid communication is capable through the passageway in the outer housing, and when the sliding sleeve is in its closed position, fluid communication through the passageway in the outer housing is restricted. When the sliding sleeve disposed within the outer housing is in its open position, fluid communication of a gravel laden slurry is permitted through the passageway in the outer housing. When the isolation tubing element is in its lower position, the sliding sleeve disposed within the inner housing is in its closed position, and the sliding sleeve disposed within the outer housing is in its closed position, the first zone of the wellbore is isolated from the wellbore located below the lower packer. When the isolation tubing element is in its lower position, the sliding sleeve disposed within the inner housing is in its closed position, and the sliding sleeve disposed within the outer housing is in its closed position, the first zone of the wellbore is isolated from the wellbore located above the upper packer.
The assembly can further comprise a gravel pack adapter releasably seated within the upper packer, the gravel pack adapter comprising a work string and a cross-over assembly, the work string being in fluid communication with the area within the outer housing above the inner housing, and the cross-over assembly being in fluid communication with the isolation tubing element. When the isolation tubing element is in its upper position, and the sliding sleeve disposed within the outer housing is in its open position, the gravel pack adapter work string is capable of communicating a gravel laden slurry through the passageway in the outer housing to the annulus area between the wellbore and the sand screen, and the cross-over assembly is capable of communicating slurry returns between the sand screen and the annulus area between the work string and the wellbore above the upper packer. The gravel pack adapter can be capable of shifting the sliding sleeve in the outer housing from an open position to a closed position upon the removal of the gravel pack adapter from the upper packer.
The assembly can further comprise a dual flow adapter releasably seated within the upper packer, the dual flow adapter comprising a first flow tubing and a second flow tubing. When the dual flow adapter is seated within the upper packer the first flow tubing is in fluid communication with the area within the outer housing above the inner housing and the second flow tubing is in fluid communication with the isolation tubing element. The dual flow adapter can be capable of shifting the sliding sleeve in the outer housing from an open position to a closed position when the dual flow adapter is inserted into the upper packer. When the isolation tubing element is in its lower position, the sliding sleeve disposed within the inner housing is in its open position, and the sliding sleeve disposed within the outer housing is in its closed position, the first zone of the wellbore is in fluid communication with the first flow tubing and the wellbore located below the lower packer is in fluid communication with the second flow tubing. The second flow tubing can be capable of shifting the sliding sleeve within the inner housing from an open position to a closed position when the second flow tubing is removed from the wellbore. The second flow tubing can be capable of shifting the sliding sleeve within the inner housing from a closed position to an open position when the dual flow adapter is placed within the upper packer.
Another embodiment of the invention is an assembly for completing a wellbore comprising an outer housing and an inner housing disposed within and attached to the outer housing. A first sliding sleeve is disposed within the outer housing capable of moving between an open and closed position and a second sliding sleeve is disposed within the inner housing capable of moving between an open and closed position. An isolation tubing is at least partially disposed within the inner housing and capable of moving between an upper and lower position. A sand screen is disposed within the outer housing and located below the inner housing. When the first sliding sleeve is in its open position, a path for fluid communication between the inside and the outside of the outer housing is created and is capable of passing a gravel pack slurry. When the isolation tubing is in its upper position, gravel pack fluid returns are capable of passing through the sand screen, through the isolation tubing and to the surface.
When the isolation tubing is in its lower position and the first and second sliding sleeves are in their closed positions, the sand screen is isolated from the wellbore above the gravel pack assembly. When the isolation tubing is in its lower position and the first and second sliding sleeves are in their closed positions, the sand screen is isolated from the wellbore below the gravel pack assembly.
Yet another embodiment is a method for completing a dual well comprising completing a lower zone below a lower packer. An upper zone completion assembly is provided comprising an upper packer, an outer housing comprising a gravel pack port, a sand screen and a seating element. An inner housing comprises a production port and an isolation tubing capable of moving between an upper position and a lower position and capable of seating within a receptacle attached to the lower packer. The upper zone completion assembly is seated within the lower packer, the isolation tubing being in its upper position. The upper packer is set and the upper zone is gravel packed by flowing a gravel slurry through the gravel pack port and taking fluid returns up through the isolation tubing. The upper zone is isolated from the rest of the well by closing the gravel pack port and the production port and by lowering and seating the isolation tubing within the lower packer receptacle. Fluid communication between the lower zone and the surface can be provided through the isolation tubing.
The method can further comprise inserting a dual flow adapter connected to a first tubing string and a second tubing string into the well and seating the dual flow adapter into the upper packer. Fluid communication can be provided between the first tubing string and the lower zone through the isolation tubing and fluid communication can be provided between the second tubing string and the upper zone through the production port within the inner housing.
Still another embodiment if the present invention is a method for isolating the upper zone in a dual completion wellbore. The method provides an upper zone completion assembly comprising an inner housing, having a production port and a sliding sleeve. The sliding sleeve is capable of moving between an open position and a closed position, wherein when the sliding sleeve is in its closed position, fluid communication through the production port is restricted. The upper zone is isolated by mechanically shifting the sliding sleeve from the open position to the closed position, thereby restricting fluid communication through the production port. When the upper zone is isolated, fluid communication between the wellbore below the upper zone completion assembly and the wellbore above the upper zone completion assembly is possible through the upper zone completion assembly. The method can further comprise reestablishing upper zone production capability by mechanically shifting the sliding sleeve from the closed position to the open position, thereby enabling fluid communication through the production port.
One particular embodiment of the invention is a subterranean wellbore completion and production method for an upper zone in a dual well. The method involves providing a completion assembly comprising an inner and outer housing, a first sliding sleeve and a sand screen disposed within the outer housing. A second sliding sleeve is disposed within the inner housing along with an isolation tubing capable of moving between an upper position and a lower position that is at least partially disposed within the inner housing. The completion assembly is positioned within the wellbore with the isolation tubing in its upper position. The well is gravel packed by flowing a gravel laden slurry through the first sliding sleeve and taking fluid returns up through the isolation tubing. The isolation tubing is then lowered to its lower position. The upper zone is isolated by having both the first sliding sleeve and the second sliding sleeve in their closed positions. The method can also comprise producing the upper zone through the sand screen and through the second sliding sleeve. The lower zone can be produced through the isolation tubing. The two zones can be produced separately by producing the upper zone through the sand screen and the second sliding sleeve, and a lower zone through the isolation tubing. The outer housing can be attached to and located below an upper packer and above a lower packer. When the isolation tubing is in its lower position it seats within a receptacle attached to the lower packer.
The method can further comprise providing a dual flow adapter connected to a first and second tubing strings. The dual flow adapter is inserted into the upper packer, wherein the second tubing string is seated within the inner housing. The upper zone can be produced through the sand screen, the second sliding sleeve, and the first tubing string. The lower zone can be produced through the lower packer, the isolation tubing, and the second tubing string.